SUMMARY: V.32BIS / Sun workstation problem

From: Chris Osicki (
Date: Fri Dec 11 1992 - 10:03:37 CST

My original posting:

>Configuration: Zyxel U-1496 modem connected on ttya (tty speed set to 38400)
> Sun ELC & Sun IPC, SunOS 4.1.2

>When a connection is made at 14400, V.42, V.42BIS many characters are 'lost'.
>Connecting a vt220 directly to the modem instead of the ELC no characters
>are lost. Is this a known problem in that Suns serial ports cannot handle
>data at high speeds? If yes, are there any solutions (H/W or S/W) which
>solve this.

The explanation (not solution) of this problem is easy:
the serial port driver 'zs' doesn't support correctly hardware flow control.
To be more precise, 'zs' only does CTS flow control - stops sending when modem
drops CTS, but does not drop RTS when data from modem arrives to fast.
This is a fact, and our SUN support confirmed this ! The people who believe
in Sun's hardware flow control and didn't see any problems are lucky.

Now the possible solutions:

1. Sun offered me a High Speed Serial I/O card for sFr 5490 ( ~ 4000 $, it is
   not an april fool, yes, four thousand dollars )

2. SUN's high-speed serial driver for up to 38.4 Kbps. I didn't get the price
   from SUN support yet, but the prices I have heard about are:
   $950/cpu, $2850 for 10 and $5700 for a site license.
   This also sounds like a joke but is not one.

3. Get a third party serial S-bus expansion board. I don't have any info yet
   but I know they exist, and I could imagine the cost would be something between
   10 * PC-I/O card and 1/10 of SUN High Speed card.
4. Write your own serial port driver ( send me a copy ;-) )

5. Use software flow control XON/XOFF. It works for me.

6. Other possible solutions have nothing to do with SUN and thus with this
   news group ;-).
Our SUN support told me that the maximum supported serial port speed is
9600 bps. This speed seams to be for SUN the state of the art. Pay if you want
more. Once more SUN try to sell us something that should be part of the system.

If you are interrested in all the replies I received, let me know and I will
make them ftpable.

Thanks once more to all who replied. I tried to thank everybody by mail,
hope I didn't miss anyone.


   Chris Osicki ( )
   System and Network Administrator
   Ascom Hasler AG, Abt 85L2, Freiburgstr. 251,
   CH 3000 Bern 18, Switzerland. Tel: +41 31 999 38 07, Fax: +41 31 991 37 35

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